Radiation effects on rare earth permanent magnets

Abstract

With continuing improvements in rare earth permanent magnet (REPM) technology, applications for their use are being discovered that were previously not possible. Two such applications for permanent magnets are in focusing elements for linear accelerators and ion sources, and in insertion devices (wigglers and undulators) used to produce synchrotron radiation. However, these magnetic transport elements are subjected to high radiation levels. Consequently, there is considerable interest in the United States and abroad to discover and quantify the effects of radiation on REPMs. Using the Lawrence Livermore National Laboratory (LLNL) 100 MeV Linac, four different samples of REPM were irradiated to one to two gigarads of exposed dose from a bremsstrahlung production target in an attempt to simulate the consequences of beam spills of a high energy primary electron beam. Of the samples irradiated, Sm2Co17 proved to be the most resistant to gamma radiation. The electron transport code CYLTRAN of the Integrated Tiger Series (ITS), which is an electron and photon Monte Carlo simulation code, was used to determine the angular and energy spectra for both electrons and photons produced by the target used at the LLNL Linac